The remains of a trumpeter swan that was among 32 found dead in western Clinton County is being tested at the Iowa State University vet lab to determine the cause of death.

The remains were discovered Jan. 30 on a privately owned wetland area by a hunter.

At first it appeared that the carcasses had been so cleanly scavenged that there was not enough tissue available for testing, but a subsequent walk-through uncovered one complete carcass and two partials, said Mark Roberts, of Clinton County Conservation.

The remains were turned over Tuesday to the Veterinary Diagnostic Laboratory in Ames, Curt Kemmerer, a DNR wildlife biologist, confirmed.

"It's shocking," Roberts said of the deaths. "I've never heard of anything like this."

Trumpeter swans are a native species that nested throughout Iowa before European settlement, but were decimated to the brink of extinction by hunting and drainage of wetlands.

In 1993, the DNR developed a plan to restore trumpeter swans and in 1998, the first modern-day hatch of three wild cygnets occurred in Dubuque County. The population is growing slowly with 54 nesting pairs recorded in Iowa this year, David Hoffman, a research technician with the DNR, said.

Statewide, the leading causes of trumpeter swan death are illegal shootings, lead poisoning, powerline collisions and disease, according to the DNR.

Swans can be poisoned by lead if, while searching wetland sediment for grit — tiny pieces of rock or shells that help them digest food — they happen to pick up lead shot, or pellets, instead.

Lead shot was banned for waterfowl hunting in 1991, but its use for upland hunting, shooting sports and in fishing tackle remains widespread, and it persists for years in the environment, according to the DNR.

The remains that were delivered to Ames were found by Kelly McKay, a self-employed wildlife biologist from Hampton. He is familiar with the wetland site because it is one of the places he has visited for years as part of the Christmas Bird Count, an annual counting of birds sponsored by the National Audubon Society.

When McKay visited the site northwest of Toronto during the count on Dec. 18, he tallied 68 trumpeter swans. When he returned to look for the carcasses, there were no living swans. However, that was to be expected because the water was frozen over, which would have driven them out, McKay said.